Selecting the face of any Olympics is a pointless act; the Games are many things. Here in Brazil, the games are soccer and Neymar. In the United States, they could be Simone Biles or Simone Manuel or Diana Taurasi. Or they could be any of the dozens of remarkable athletes who won gold medals here away from the attention of NBC’s—or anyone’s—cameras. The Olympics, whether in Brazil or China or England or the United States, are a sprawling enterprise that affects every person in a different way.

Still. Bolt and Phelps live alone in their own, private Olympic Village. It has a gate and 24-hour security, and there is nothing for sale in the entire complex. They became giant celebrities together in 2008, and have taken a place in the Olympic Games that is theirs alone. The debate over whether either of them is the “greatest Olympian ever,” is pointless. Apples and oranges, and over the life of the Games, more other fruits and vegetables that you can gather. There is no greatest Olympian ever. But if you have watched the Olympics from 2008-16, and someday you are asked what you remember most, there’s a good chance you will say Usain Bolt. Or Michael Phelps. (Yes, surely the latter answer trends toward Americans. Bolt is a worldwide celebrity, adored in the United States and in places where Phelps is barely known at all; but America is a big place and this is an American publication.)

Both Bolt and Phelps declared—before and after competition—that Rio would be their last Olympics. Neither waffled, unless you count Phelps opening the door a crack in a press conference before the Games (he slammed it shut afterward).

“Done,” said Phelps, with his 23 gold medals and 28 overall medals. “I am not coming back in 2020.”

“No,” said Bolt, with his unprecedented three consecutive wins in the 100, 200 and 4×100-meter relay. “There’s nothing else for me to do.”

There are many reasons to believe both men, but that will do nothing to prevent speculation about comebacks. (Also, while Phelps is retired, Bolt is planning to run another year on a truncated schedule and compete in the 100 meters at the 2017 world championships next summer in London). I think it’s overwhelmingly likely that neither man competes in Tokyo in four years, but I also think it’s slightly more overwhelmingly likely that Bolt does not compete. Slightly. Here’s why:

• Bolt is going to be better at retirement than Phelps. He’s going to be better at retirement than most people. Bolt is a fierce competitor on the line, but his avowed disdain for 11 months of six-day-a-week training is genuine. Bolt told me last spring, “I’ve been telling people for years that I’m a lazy person, and I don’t think they believe me. But I really am. I don’t like the training.” He really doesn’t like the training. And he’s also not crazy about the madness that attends his participation in a global championship. “I’m not going to miss the interviews,” said after his final relay. “I’ve done about 500 interviews since I’ve been here.”

Phelps, meanwhile, has always been most at home in the pool. That reality was too extreme for many years and Phelps famously struggled with life on dry land. But after the life change that followed by 2014 DUI arrest, Phelps didn’t need the water as much, but somehow liked it better. He is an immense celebrity in the United States, and crosses over into the People universe. But there is an Ali-like quality to Bolt that makes his public life more claustrophobic than Bolt’s. It’s grading at the top of the curve, but I would argue that Bolt is a bigger public figure and by nature, more inclined to seek lasting escape from the public, except on his terms.

• Phelps’s dominance might have more legs. Phelps won two individual races in Rio, the 200-meter butterfly by .04 on the wall and the 200-meter individual relay by nearly two seconds, a huge margin. He was soundly beaten in the 100-meter butterfly by 21-year-old Joseph Schooling. But it’s easy to imagine that, with a lesser program—fewer individual events, fewer relays—Phelps could sustain control of at least one event. His drop-off is subtle and seemingly manageable.

Bolt won the 100 meters in 9.81 seconds, comfortably in front of Justin Gatlin of the U.S.A. (9.89) and 21-year-old Andre de Grasse of Canada (9.91). He struggled much more in the 200 meters, where he tried very hard to run fast but managed only 19.78. That was good enough for a .24 margin over de Grasse, but even Bolt admitted that when he reached for speed, his legs said no. This is partly because Bolt missed two weeks of important training in early July with a hamstring and low back injury, but it’s also because, while he is only 30 years old, he’s been sprinting at the top level in the world since he was 17 years old.

Bolt turned 30 only on Sunday, but he is much older in sprinter years. He wasn’t appreciably threatened in either of his individual events, but there’s no reason to think that he’s ever going to run faster again. There is no Bolt (no Gatlin, no Yohan Blake, no Tyson Gay, no Asafa Powell) on the horizon. Times in the low 9.8s might again win championships, but it’s reasonable to wonder if Bolt has the legs or the desire to run that fast in four years.

Phelps was in the Olympics at 15, but has taken several extended breaks from swimming, notably after the 2008 and 2012 Olympics. He was behaving badly on those breaks, but he wasn’t training 80,000 meters a week in a swimming pool, grinding on his balky right shoulder. Bolt’s lower back and hamstring need constant supervision and his training is often customized to limit the possibility of injury.

Neither man is wanting for money, although Bolt’s earning power has never been dented by scandal. It’s almost certain that their primary sponsors will stay in place long after both men have stopped competing. They are brand names. IAAF president Sebastian Coe has asked Bolt to stay close to the sport, capacity to be determined. “Not in coaching,” says Bolt. That would be too much like competing, what with all the practices and such. He has business interests in Jamaica.

Phelps has already started a family and says he and his fiancée will have more children past Boomer. He has his foundation and will surely consider broadcasting (although there’s not a lot of televised swimming). Both men will find life a little less exciting, but that’s common to all athletes. See above: Bolt is better suited to this than Phelps. But Phelps might be just fine. He seemed to be at peace upon leaving Rio. Bolt seemed euphoric.

And there is this: The culture will prod them for more, but neither man owes the Olympics another moment. Their records will endure for years, their names for as long as the Games are contested. They won’t be replaced.